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pipeline_handler: Add acquireDevice() function to mirror releaseDevice()

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libcamera always keeps all /dev/video# and /dev/v4l2_subdev# nodes for a
pipeline open after enumerating the camera.

This is a problem for the uvcvideo pipeline handler. Keeping /dev/video#
open stops the UVC USB device from being able to enter runtime-suspend
causing significant unnecessary power-usage.

Add a stub acquireDevice() function to the PipelineHandler class which
pipeline handlers can override.

The uvcvideo pipeline handler will use this to delay opening /dev/video#
until the device is acquired. This is a special case because the kernel
uvcvideo driver powers on the USB device as soon as /dev/video# is
opened. This behavior should *not* be copied by other pipeline handlers.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Harvey Yang <chenghaoyang@chromium.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
This commit is contained in:
Hans de Goede 2024-08-30 13:12:05 +02:00 • committed by Laurent Pinchart
parent 9020c2eec9
commit c05e45ac77
3 changed files with 43 additions and 10 deletions
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3
include/libcamera/internal/pipeline_handler.h
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@ -45,7 +45,7 @@ public:
MediaDevice *acquireMediaDevice(DeviceEnumerator *enumerator,
const DeviceMatch &dm);
bool acquire();
bool acquire(Camera *camera);
void release(Camera *camera);
virtual std::unique_ptr<CameraConfiguration> generateConfiguration(Camera *camera,
@ -79,6 +79,7 @@ protected:
virtual int queueRequestDevice(Camera *camera, Request *request) = 0;
virtual void stopDevice(Camera *camera) = 0;
virtual bool acquireDevice(Camera *camera);
virtual void releaseDevice(Camera *camera);
CameraManager *manager_;